1. Field of the Invention
The present invention relates generally to a parallel-operated hydraulic motor type stern propulsion apparatus for boats and a hydraulic system for controlling the same, in which propellers are driven by two parallel-operated hydraulic motors, and the sailing speed of a boat and the forward and rearward drives and steering and lifting angles of the stern propulsion apparatus are remotely controlled.
In particular, the present invention relates to a parallel-operated hydraulic motor type stern propulsion apparatus for boats and hydraulic system for controlling the same, in which the control of steering and lifting angles can be performed by a hydraulic system for the stern propulsion apparatus, the mounting position of a main engine can be freely selected to allow the cabin of the boat to be conveniently designed. This apparatus comprises hydraulic power system and control system, one transom box, one upper body, one yoke and two lower bodies. Furthermore, this apparatus can improve its durability by the parallel-operation of propellers with an hydraulic system for the controlling of reversing, the starting and stopping of the main-engine, for the manueuvering of sailing speed, the reversing operation of the boat and steering and lifting angles of the stern propulsion apparatus hydraulically.
2. Description of the Prior Art
In a conventional stern propulsion apparatus for boats and hydraulic system for controlling the same, a main engine operates a propeller via a reduction gear, a clutch, a reverse gear and a propeller shaft. Accordingly, when the propeller is brought into a submerged projection or floating matters, or seaweed is wound around the propeller, its power train and its main engine are damaged, thereby causing a boat to run into serious danger. Additionally, a steering device for steering the boat to the right and left and a lifting device for adjusting the stern propulsion apparatus to a proper height depending variations in the depth of the sea are controlled by an independent hydraulic system, so the cost of the stern propulsion apparatus and hydraulic system are increased. Furthermore, when the conventional stern propulsion apparatus for a boat sized 6 tons or less is designed to generate 300 horsepower so as to meet the recent demand for high speed boat, the output of its hydraulic motor is enlarged, thereby increasing the hydrodynamic resistance of the stern propulsion apparatus.
Furthermore, in the conventional stern propulsion apparatus driven directly by a main engine, a lifting angle is restricted to 60xc2x0 or less and breakdown easily occurs owing to the necessity for additional reduction gear and reverse gear additionally.
The main object of the present invention is to provide a parallel-operated hydraulic motor type stern propulsion apparatus and hydraulic system (main pump 1 set, motor 2 sets) for controlling the same, which is capable of reducing the hydrodynamic resistance of the apparatus that causes 80% of the required power, by employing two hydraulic motors each having parallel-operated propellers.
Another object of the present invention is to provide a parallel-operated hydraulic motor type stern propulsion apparatus and hydraulic system for controlling the same, which is capable of reducing the mounting area, installation costs and weight of the stern propulsion apparatus, utilization of propulsion energy effectively and simplifying the hydraulic system, by supply working fluid from the same hydraulic system for driving propeller to steering and lifting devices.
In order to accomplish the above object, the present invention provides a parallel-operated motor type stern propulsion apparatus for boats, comprising: a transom box disposed at the stern wall of a boat; a propulsion body situated in the transom body to be lifted and steered, the propulsion body including, an upper body supported by a lifting shaft transversely fitted into the transom box, a yoke connected to the upper body, and two lower bodies attached apart to the both (port and starboard) lower ends of the yoke: two hydraulic motors each positioned in each of the lower bodies (port and starboard) and each connected to a propeller via each propeller shaft; lifting cylinders attached to the transom box for lifting the propulsion body around the lifting shaft; and a steering cylinder attached to the transom box for steering the propulsion body around a steering pin attached to the lifting shaft toward the starboard and port side.